The present invention relates to digital printing apparatus, such as an ink-jet or electrostatographic xe2x80x9claser printer,xe2x80x9d which prints images based on image data originating in a computer data file.
Digital printers, which print images such as documents which are retained as data files in computers, are now commonplace in offices. In the standard model of digital printing, data to be printed is retained in the memory of what will here be called a xe2x80x9csource computer,xe2x80x9d which may be of any type, such as a print driver, print server, personal computer, or mainframe. When the data to be printed, in the form of a file, is sent from the source computer to a printer, the data is in a page description language (such as PCL or Adobe(copyright) PostScript(trademark)) or some other format, such as TIFF or a fax format such as CCITT. At the printer, software resident therein known as a xe2x80x9cdecomposerxe2x80x9d or xe2x80x9cinterpreterxe2x80x9d converts the file from its original page description language or format into code which ultimately operates the printer hardware, such as by modulating a laser or controlling an ink-jet printhead over time, to form the desired printed images.
In real-world situations, certain practical limitations of both source computers and printers must be taken into account. With particular relevance to the present invention, certain types of printers from various manufacturers may be inherently incapable, by virtue of their basic design, of printing images on an entire sheet which passes therethrough. Rather, printed images from such printers can be no larger than slightly less than the total area of the sheet: the edges of each sheet will not be able to be printed upon. This phenomenon, which is known as xe2x80x9cedge deletion,xe2x80x9d is fairly common with inexpensive printers. In such cases the edge deletion extends by about xc2xc inch on at least two sides of each printed sheet. With regard to different types of source computers, certain computers, such as legacy mainframes, may consistently provide image data to a printer which is subject to image deletion and a bad consequence thereof. For example, if a mainframe regularly outputs a spreadsheet in small type and with rudimentary formatting to a printer, if the printer is incapable of printing to the edge of a sheet, it is likely that an entire row or column of the spreadsheet may be deleted.
According to one aspect of the present invention, there is provided a method of printing an image based on digital image data, the digital image data including a header. The header is searched for a data string which identifies the digital image data as originating from an accepted source computer. If the data string is not in the header, an alteration is performed on the image data, the alteration having an effect of causing a printed image resulting from the data to avoid an edge of a print sheet on which the printed image is printed.